As a method for controlling those weeds belonging to the genus Cyperus in Cyperaceae which are major weeds growing in the paddy fields and fields, a method using chemical herbicides is mainly employed. Recently, in view of the problem of environmental pollution caused by abundant use of agricultural chemicals, the development of herbicides not depending on agricultural chemicals and methods for using the same is desired In particular, the development of microbial herbicides using a plant pathogenic fungus are highly expected. To date, DeVine (U.S.A.; target weed: Stranglervine, Asclepiadaceae), Collego (U.S.A.; target weed: Northern jointvetch, Leguminosae) and BioMal (Canada; target weed: Round-leaved mallow, Malvaceae) have been registered as herbicides and commercialized. However, there has not been developed a microbial herbicide targetted at weeds belonging to the genus Cyperus in Cyperaceae.